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  17242   Tue Nov 8 10:35:26 2022 AnchalUpdateSUSIMC F2A test

This time the test was succesful but I have reverted MC3 f2a filters back to with Q=3, 7, and 10. The inital part of the test is still useful though. I'm attaching amplitude spectral density curves for WFS control points and C1:IOO-MC_F_DQ in the different configurations. The shaded region is the 15.865 percentile to 84.135 percentile bounds of the PSD data. This corresponds to +/- 1 sigma percentiles for a gaussian variable. Also note that in each decade of freqeuncy, the FFt bin width is different such that each decade has 90 points (eg 0.1 Hz bin width for 1Hz to 10 Hz data, 1 Hz binwidth  for 10 Hz to 100 Hz and so on.)

The WFS control points do not show any significant difference in most of the frequency band. The differences below 10 mHz are not averaged enough as this was 30min data segments only.

C1:IOO-MC_F_DQ channel also show no significant difference in 0.1 Hz to 20 Hz. Between 20-100 Hz, we see that higher Q filters resulted in slightly less noise but the effect of the filters in this frequency band should be nothing, so this could be just coincidence or maybe the system behaves better with hgiher Q filters. In teh lower frequency band, we would should take more data to average more after shortlisting on some of these f2a filters. It seems like MC1 Q=10 (red curve) filter performs very good. For MC2, there is no clear sign. I'm not sure why MC2 Q=3 curve got a big offset in low frequency region. Such things normally happen due to significant linear trend presence in signal.

I'm not sure what other channels might be interesting to look at. Some input would be helpful.

Attachment 1: IMC_f2a_test_results.pdf
IMC_f2a_test_results.pdf IMC_f2a_test_results.pdf IMC_f2a_test_results.pdf IMC_f2a_test_results.pdf IMC_f2a_test_results.pdf IMC_f2a_test_results.pdf IMC_f2a_test_results.pdf
  17241   Tue Nov 8 10:23:42 2022 AnchalUpdateSUSMC3 damping loop step responses

I tuned MC3 local damping gains by looking at step responses in the DOF bassis. The same procedure was followed as described in 40m/17133. The gains were changed as following:

  Old Gains New Gains

Attachement 1 shows the step responsed with the old gains and attachment 2 shows the step responses with the new gains. There is considerable cross coupling between SIDE OSEM and Coil to the face DOFs (POS, PIT, YAW). I think the high SIDE gain earlier was the culprit that started ringing with the f2a filters.

I agree that POS and SIDE step responses could look better but this was the best I was able to achieve. Further attempts by others is most welcome.

I also verified running f2a filter with Q=3 and it has been stably running with no ringing for past few minutes. More long term behavior is yet to be seen.C1:SUS-MC3_SUSSIDE_GAIN

Attachment 1: MC3_Step_Response_Test_2022-11-08_09-48.pdf
MC3_Step_Response_Test_2022-11-08_09-48.pdf MC3_Step_Response_Test_2022-11-08_09-48.pdf MC3_Step_Response_Test_2022-11-08_09-48.pdf MC3_Step_Response_Test_2022-11-08_09-48.pdf
Attachment 2: MC3_Step_Response_Test_2022-11-08_10-19.pdf
MC3_Step_Response_Test_2022-11-08_10-19.pdf MC3_Step_Response_Test_2022-11-08_10-19.pdf MC3_Step_Response_Test_2022-11-08_10-19.pdf MC3_Step_Response_Test_2022-11-08_10-19.pdf
  17240   Tue Nov 8 08:57:18 2022 ranaUpdateSUSMC2 OSEMs calibrated using MC_F

this measurement is not valid because of the coil to sensor coupling that I mentioned before. This is why I suggested you make the measurement at low frequencies (like 0.1 Hz).


MC2 OSEM outputs were calibrated today using MC_F to get the output values in microns. This was done using this diaggui file. We drive a sine wave at 13 Hz and 5000 cts at C1:SUS-MC1_BIASPOS_EXC.

  17239   Mon Nov 7 21:57:42 2022 alexUpdateGeneralSensoray

I have made little progress in getting the sensoray driver installed on Donatella. I have confirmed that it is indeed the reason why none of the hardware is working. I am now working through changes on a virtual machine that is running Scientific Linux to find something that may work. If no progress is made soon, I will ensure that software for a replacement video encoder is able to be installed before requesting we order one.

  17238   Mon Nov 7 20:00:37 2022 AnchalUpdateSUSMC1 OSEMs output is weird

Following up, I tried to do this exercise with MC1 and MC3. While MC3 shows expected minute corrections to the previous value, MC1 showed much alrger corrections which led me to investigate further. Koji suggested to take a transfer function between MC_F and the OSEM outputs for both MC1 and MC3 the same way to see if something is different. And Koji was absolutely right. MC1 MC_F to OSEM outptu transfer function has a frequency dependent value, with a slope of ~0.6. Very weird. I'm holding on to doing OSEM calibration on both MC1 and MC3 until we know better on what is happening. See attached transfer functions.

Reminder, MC1 is using new satellite amplifier box, but OSEM outputs are read through single ended PDMon outputs rather than the differential ended PD Output port, because rest of the MC1 electronics is still last generation and the whitening board for them take in single ended input.

Attachment 1: MC1_MC_F_OSEM_TF.pdf
Attachment 2: MC3_MC_F_OSEM_TF.pdf
  17237   Mon Nov 7 19:53:12 2022 AnchalUpdateSUSMC2 OSEMs calibrated using MC_F

MC2 OSEM outputs were calibrated today using MC_F to get the output values in microns. This was done using this diaggui file. We drive a sine wave at 13 Hz and 5000 cts at C1:SUS-MC1_BIASPOS_EXC. This signal is read at C1:IOO-MC_F and the C1:SUS-MC1_ULSEN_OUT and similar OSEM output channels. MC_F calibration in Hz is assumed to be correct. In diaggui, a calibration conversion of 4.8075e-14 m/Hz is added to convert MC_F signal into meters. This is then used to calibrate the OSEM outputs and necessary gain changes were done in teh cts2um filter module in all of the face OSEM input filters. Following are the new gains:

  • UL 0.36 -> 0.28510
  • UR 0.36 -> 0.26662
  • LL 0.36 -> 0.34861
  • LR 0.36 -> 0.71575

Note that this measurement was done after the coil strengths for MC2 have been balanced in 40m/17223.

  17236   Mon Nov 7 17:10:41 2022 AnchalSummaryBHDQPD installation seems like lost cause

The new QPD installation is turning out to be much more hard than it originally seemed. After finsing the cable, QPD and interface board, when I tried to use the cable, it seems like it is not powered or connected to the interface board at all. I tried both QPD ports on the QPD interface board (D990692) both none worked. I measured the output pins of IDC style connector on the interface board and they seem to have the correct voltages at the correct pins. But when I connect this to our cable and go to the other side of the cable which is a DB25, use a breakout board and see for the voltages, I see nothing. The even pins which are supposed to be connected to each other and to GND are also not connected to each other. I pulled out teh DB25 end of the cable and brought it close to the IDC end to do a direct conitnuity test and this test failed too.

I even foudn another IDC end of a spare QPD cable hanging near 1Y2, but could not find the other end of this cable either.

So moving forward, we have following options:

  • Assume the cable is bad and try to find another cable.
    • It is very hard to find these cables in the lab. Koji and I have already done one sweep.
  • Source 26 pin 2 row IDC female connector and make a ribbon cable ourselves.
    • We probably will need to buy this connector for this to work.
    • Downs has apparantely thrown away all IDC connectors.
  • Use clean room QPD that does not use this interface.
    • The QPD used in clean room tests for suspension hanging used a different board.
    • This board is just lying on the floor, mounted on one slot of a big 6U chassis.
  • Use AS WFS
    • If used in current position, it would not be useful for BHD port or tuning LO1, LO2, and AS4.
    • If taken to ITMY oplev table, we will need to source LO and opther connections right at the PD head as that is design for these PDs.
  • Use GigE camera
    • We can replace the analog camera with a GigE camera on the BHD output.
    • We will need to revide GigE camera code and medm screens for this, and run an ethernet cable to ITMY oplev table.
  • Someone verify that the cable is indeed not working as I am seeing above. If I am wrong, I would be a happier person.
  17235   Mon Nov 7 16:14:43 2022 AnchalUpdateSUSF2A filter with Q=1, 0.3 stable with MC3

I tired running for a few hours F2A filter with Q=1 and for maybe 30 min Q=0.3 on MC3 today and that keeps the suspension stable. So I'm going to put in Q=0.3 at FM1, Q=0.7 at FM2, and Q=1 filter on FM3. I am setting the test again for tonight with some modifications. Now the separate set of filters will be tried one by one on the three different optics so that we know the best Q filter for each optic. It is set to trigger at 1 am tonight in tmux sessions f2aMC1Test, f2aMC2Test, f2aMC3Test on rossa. To cancel the test or interrupt, do:

tmux a -t f2aMC1Test
tmux a -t f2aMC2Test
tmux a -t f2aMC3Test
  17234   Mon Nov 7 14:38:59 2022 AnchalUpdateSUSMC3 coil strengths rebalanced

I checked again today by sending excitation at POS and reading back from C1:IOO-MC_TRANS_P and C1:IOO-MC_TRANS_Y. I found that there was some POS->PIT and POS->YAW coupling remaining that I was to remove by same method. New coil gains are:



  17233   Mon Nov 7 12:37:26 2022 KojiUpdateGeneralBorrowed the fiber tester for the OMC lab

I am borrowing the fiber illuminator / fiber tester / VisiFault for the OMC lab. It has been stored in the top drawer at the center work bench.

==> Returned

Attachment 1: PXL_20221107_202016688.MP.jpg
  17232   Mon Nov 7 12:02:15 2022 AnchalUpdateSUSIMC test with PSL shutter closed.

Following configurations were kept today morning:

Start Time Stop Time HEPA PSL Shutter MC1 f2a MC2 f2a MC3 f2a MC3 ringing Notes


10:04:45 PST
18:04:45 UTC


10:09:39 PST
18:09:39 UTC

ON OFF ON ON ON NO Found later that MC3 started ringing at 1351879797


10:09:39 PST
18:09:39 UTC


10:35:07 PST
18:35:07 UTC

ON OFF ON ON ON YES This is the duration when MC3 was ringing


10:35:07 PST
18:35:07 UTC


10:50:39 PST

OFF OFF ON ON ON YES We turned off HEPA filter during this time, MC3 was still ringing.


10:50:39 PST
18:50:39 UTC


10:52:08 PST
18:52:08 UTC

OFF OFF ON ON ON NO I noticed MC3 rining and reset f2a filter by turning it off, waiting for it to damp down and restarting it.


10:52:08 PST
18:52:08 UTC


11:09:48 PST
19:09:48 UTC

OFF OFF ON ON ON YES MC3 started ringing again soon.


11:09:48 PST
19:09:48 UTC


11:44:32 PST
19:44:32 UTC

OFF OFF ON ON OFF NO MC3 f2a filters turned off due to repeated failure.


11:44:32 PST
19:44:32 UTC


12:17:49 PST
20:17:49 UTC

ON OFF ON ON OFF NO Turned ON HEPA for completeness of data.


  17231   Mon Nov 7 11:24:05 2022 AnchalUpdateSUSF2A filters on MC1, MC2, and MC3 set to test at 1 am

This test was not successfull as IMC lost lock during the f2A filter trial. However, we do have 1 hour off data when all f2A filters were turned off in between following GPS times:

start gpstime: 1351584077

stop gpstime: 1351587677

After this gpstime, the f2A filters were turned ON for all IMC optics. After about 2000 seconds of no issues, the MC3 suspension suddenly rung up 1 Hz oscillations around 1351590720 gpstime. See attachment one for noise spectra of local damping error signals for MC3 before and after this event. See attachment 2 for time series of this event.

So, after this point, MC3 remained rung up and IMC remained unlocked, so no WFS signals are meaningful after gpstime 1351590720.

I have seen this happening out of nowhere to MC3 today too when PSL shutter was closed and only thing interacting with MC3 was the local damping loop. This suggests that some glitch event happens in MC3 which is not taken well by the f2a filter on it. The ringing goes down as soon as we turn OFF the f2a filter. The other optics show no such signs.

We'll do more tests in future to figure out the issue. For now, MC3 f2a filters are kept off. Maybe we need custom filter for MC3 rather than the design value default filter we are using right now. I'm attaching foton bode plot for MC3 f2a filters for verification that correct filters are in place.

Attachment 1: MC3_f2a_failure_analysis.pdf
Attachment 2: MC3_f2a_Failure_Event.png
Attachment 3: MC3_f2aQ3_filters.pdf
  17230   Mon Nov 7 08:36:10 2022 JCUpdateSUSIMC out of alignment -- f2A failure

[Paco, JC]

We came in this morning and noted the IMC was grossly misaligned, with MC3 still damped but with >= 100 rms motion in all coil monitors no (a lot but not enough to trip the WD)... Turning off the WFS didn't do much so it was obviously an issue with the recent f2A output filters, so we turned all off (though only MC3 had this excess motion). After this we aligned IMC, engaged the lock and turned WFS back on.

There was no elog about f2A beyond this test scheduled to run Friday, I guess the filters were meant to stay on long term?

  17229   Fri Nov 4 15:43:05 2022 JCUpdateLab OrganizationNew Toolbox Organization

The new tool box has came in! I have spent serious time organizing these tools and making it look pretty, so please take care of it! A few things I would like to note.

  • The tool box has a power strip, so this is now where we will be charging the power tools. There is also a selected cabinet for the fully charged batteries, bits, and the power tools themselves. 
  • The cart next to the tool box had to turned 90 degrees in order to fit the tool box in. While moving this, I noticed this cart is piled with random stuff, let’s tackle this on Wednesdays clean up.
  • The tools from this tool box are specifically assigned to the VERTEX area (and the X-End until we get another toolbox.) Please return all the tools in their right tool box and cabinet after usage. 
  • The heavier duty equipment such as pipe wrenches, hammers, and power tools will remained stored here in the bottom cabinets. 

Hope you all like it!

Attachment 1: IMG_6405.JPG
  17228   Thu Nov 3 20:07:01 2022 AnchalSummaryBHDAS1 coil balancing required

[Anchal, Koji]

The LO phase lock that was achieved lasts for a short time because as soon as a considerable POS offset is required on AS1, the POS to PIT coupling causes the AS-LO overlap to go away. To fix this, we need to balance the coil outputs of AS1 atleast and add the f2a filters too. To follow similar method as used for IMC optics, we need a sensor for true PIT and YAW motion of AS1. Today, we looked into the possiblity of installing a QPD at BHD output path to use it for AS1, AS4, LO1, LO2, SR2, PR2 and PR3 coil strength tuning. We found a QPD which is mentioned in this elog. We found QPD interface boards setup for old MCT and MC Refl QPDs (dating before 2008). We also found the old IP-POS QPD cable between 1Y2 and BS Oplev table. We took out this cable from BS oplev end upto ITMY opleve table, put on a new DB25 connector on the ribbon cable, and connected it to the QPD on ITMY table. There is still following work to be done:

  • Move back the BHD port camera a few inches and the lends with it.
  • Put a beamsplitter in the beam going to this camera and align it to fall on the new QPD.
  • Connect the the other end of cable to QPD interface board on 1Y2.
  • Take the lemo outputs or IDC outputs from the QPD interface board to spare ADC inputs (maybe on LSC I/O chassis or SUS2 I/O chassis).
  • Make changes in RTS model to read this QPD input.
  • Enjoy balancing the coils on the 7 new suspensions.
  17227   Thu Nov 3 17:36:00 2022 AnchalUpdateSUSF2A filters on MC1, MC2, and MC3 set to test at 1 am

 I'll setup some test of switching between different Q filters in future.

The f2A filters are set to test on IMC optics. The script used is testF2AFilters.py. The script is running on rossa in a tmux session named f2aTest. It will trigger at 1 am, Nov 4th 2022. First the script will turn off all F2A filters on IMC optics, wait for an hour, then it will try out the three F2A filter sets with different Q values, one at a time, for one hour each. So the test should last for roughly 4 hours. The gpstime stamps will be written in a logfile that can be used later to readback noise performance of IMC with different filter. The script has a try-except failsafe to revert things to original state if something fails. To stop the script from triggering or stop it during runtime, do following on rossa:

tmux a -t f2aTest


  17226   Thu Nov 3 17:01:47 2022 ChrisUpdateCDSSLwebview fixed

The simulink webview generation cronjob on megatron was not working, apparently due to a matlab license problem. I switched it to matlab 2019a (the current CDS standard), and added a script to generate medm screens from the webview. This can help with keeping hand-made screens up to date, or be a substitute for hand-made screens if the model is simple.

  17225   Thu Nov 3 16:22:11 2022 AnchalUpdateSUSMC3 coil strengths balanced

Balanced MC3 coil strengths using the same method.

Final coil strengths found:



  17224   Thu Nov 3 16:00:58 2022 alexSummaryGeneralSensoray updates

I am currently working on getting the driver reinstalled on Donatella for the sensoray. An issue keeps arising that will not allow me to run "make" successfully in the unzipped driver folder. Will continue to remedy this.

This is why there is no light showing up on the device while plugged in. The computer does see the device, but does not show its model due to the inability for it to communicate without the driver.



  17223   Thu Nov 3 14:42:57 2022 AnchalUpdateSUSMC2 coil strengths balanced

Balanced MC2 coil strengths using the same method.

Final coil strengths found:


  17222   Thu Nov 3 14:00:29 2022 AnchalUpdateSUSMC1 coil strengths balanced

I balanced the face coil strengths of MC1 using following steps:

  • At all points, keep sum(abs(coil_gains)) = 4
  • After reading coil gains, remove the signs. Do the operations as below, and before writing put back the signs.
  • Butterfly to POS decoupling:
    • Drive butterfly mode at 13 Hz using LOCKIN2 on MC1 and look at C1:IOO-MC_F_DQ for position fluctuations
    • Subtract 0.05 times the BUT vector to coil strengths to see the effect on C1:IOO-MC_F_DQ using diaggui exponential averaging of 5, BW=1.
    • Use Newton-Raphson from here to reach to no POS actuation when driving butterfly mode.
  • POS to PIT decouping:
    • Drive LOCKIN2 in POS mode at 13 Hz and look for PIT signal at C1:IOO-MC_TRANS_P_DQ using diaggui exponential averaging of 5, BW=1.
    • Subtract 0.05 times the PIT vector to coil strengths
    • Use Newton-Raphson from here to reach to no PIT actuation when driving POS.
  • POS to YAW decoupling:
    • Drive LOCKIN2 in POS mode at 13 Hz and look for YAW signal at C1:IOO-MC_TRANS_Y_DQ using diaggui exponential averaging of 5, BW=1.
    • Subtract 0.05 times the YAW vector to coil strengths
    • Use Newton-Raphson from here to reach to no YAW actuation when driving POS.

By the end, I was able to see no actuation on POS when butterfly is driven with 30000 counts amplitude at 13 Hz. I was able to see no PIT or YAW actuation when POS is driven with 10000 counts at 13 Hz.

Final coil strengths found:


I used this notebook while doing the above work. It has a couple of functions that could be useful in future while doing similar balancing.


  17221   Wed Nov 2 16:34:56 2022 PacoSummaryCalibrationSingle arm calibration run

[Anchal, Paco]

We added a notch filter on ETMY (the actuation point of the YARM control loop) to inject our calibration line at 575.170 Hz. The excitation is injected using the DARM Oscillator, with an exc. gain of ~ 500 (this gets us a decent > 10 SNR line in the ALS Y beat). With the arm cavity locked to the PSL (~150 Hz control bandwidth), and the aux laser locked to the cavity (~10 kHz control bandwidth) the goal of this run is to calibrate our actuator strength and more importantly to budget its uncertainty. For this we have looked at the ALS beat stability using Allan statistics; we noticed the ALS beatnote frequency fluctuations start to become dominated by 1/f (or divergent noise due to systematic drifts in the YARM loop) after 10 seconds (see Attachment #1) (we have managed to see 30 seconds stability with the HEPAs off and without locking to IMC).

Our prediction is that our demodulated calibration lines will display the least residual rms noise when averaging down to around this time. This is the only reason one would use allan statistics; to quantify the separation between statistical and systematic effects in a frequency measurement. To be continued...


  • 1351464997 to 1351467139
  • 1351467259 to 1351468221
  • 1351468318 to ...
Attachment 1: frac_adev_demod_ybeat.pdf
  17220   Tue Nov 1 17:59:23 2022 AnchalUpdateSUSAdded F2A filters on MC1, MC2, and MC3

I've cleared all old attempts on F2A filters on MC1, MC2, and MC3, and added the default F2A filter described in the last post. I added 3 such sets of filters, with Q=3, 7, and 10. I have turned on Q=3 filter for all IMC optics right now. I'll setup some test of switching between different Q filters in future.

  17219   Tue Nov 1 17:17:27 2022 AnchalUpdateSUSModified F2A filter design and trial on MC1

After a quick discussion with Yuta, we figured that the introduction of a finite Q that Peter Fritschel does in this DCC doc T010140 for the poles pair, he should have done the same for the zeros pair as well otherwise there will be a notch at around 1 Hz. So I simply modified the filter design to have same Q for both zero pair and pole pair and got following transfer functions:

For upper coils:

T(s) = \frac{s^2 + s\omega_0\sqrt{1 + h/D}/Q + \omega_0^2(1+h/D))}{s^2 + s\omega_0/Q + \omega_0^2}

for lower coils:

T(s) = \frac{s^2 + s\omega_0\sqrt{1 - h/D}/Q + \omega_0^2(1-h/D))}{s^2 + s\omega_0/Q + \omega_0^2}

Attachment 1 shows the new filter design. I tested this filter set on MC1 and the optic kept on going as if nothing changed. That is atleast a good sign. Now next step would be test test if this actually helped in reducing the POS->PIT coupling on MC1, maybe using WFS signals.

The filters were added using this createF2Afilters.py script.


Attachment 1: 20221101_MC1_F2A_Filters_Q_On_Both.pdf
  17218   Tue Nov 1 15:41:18 2022 AnchalUpdateSUSF2A filter design and trial on MC1

Following discussion in this elog thread (40/6004), I used the design of F2A (force to angle(pitch)) decoupling filter as mentioned in this DCC doc T010140. This document is very useful as it talks about the overall control loops of a suspension, including sensor signal conditioning, damping filter shapes, force to pitch decoupling, pitch to position decoupling, and coil strength balancing. In future, if people are working on suspension characterization and damping, this document is a good resource to read.

Force to Angle (Pitch) decoupling filter

The document address this problem with first principle calculation using the geometry of single suspensions. As a first pass, I decided to use the design value of these geometric paramters to create a filter design for upper coils and one for lower coils. The parameters are listed in table 2. I used following:

  Description Value used
L Vertical dis-tance  from  the  suspension  point  to  the  wire  take-off  point 247.1 mm
h Pitch distance (distance above the center-of-mass of the wire take-off point) 0.9 mm
l L + h 248 mm
D Vertical distance from a magnet to the center of the optic 24.7 mm
Q Q value used in poles of the filter (doc says to use 1000) 3, 5, 10
\omega_0 Position resonant angular frequency given by \sqrt{g/l} 6.288 rad/s

Using above parameters, we can define the F2A filter for upper coils as:

T(s) = \frac{s^2 + \omega_0^2(1 + h/D)}{s^2 + s \omega_0 /Q + \omega_0^2}

and for lower coil:

T(s) = \frac{s^2 + \omega_0^2(1 - h/D)}{s^2 + s \omega_0 /Q + \omega_0^2}

I used the design values as listed in the table above and got the filters as shown in attachment 1 for Q=3 case. I think the Q is higher than what other f2a filters I have seen for example at ETMY, the filters are as shown in attachment 2.

I tried turning on MC1 f2a filters but the watchdog tripped in about 4 minutes. This was the case when WFS were turned off. Another trial also lead to the same result. I tried this on MC2 and MC3 as well, all of them tripped after som time. See attachment 3 to see MC1 tripping on these filters.

I'll now try to use a lower Q filter.

Attachment 1: 20221101_MC1_F2A_Filters.pdf
Attachment 2: ETMY_F2A_Filters_Already_There.pdf
Attachment 3: MC1_F2A_Test.png
  17217   Mon Oct 31 21:04:43 2022 KojiUpdateASCWFS inspection

Inspected the lab to see what we can do about the IFO WFS:

  • WFS heads
    • 1 functional WFS head (tuned at 11/55MHz) @AS Table [40m ELOG 15736]
    • 1 WFS head case (empty) @Section Y10 below the tube, plastic box
    • 2 WFS PCBs, components stuffed, tuning freq unknown @Section Y10 below the tube, plastic box
  • Deomdulators
    • no 4ch IQ demod unit (some component possibly spare)
    • Build 4 iLIGO demods?
  • Whitening / AA
    • No permanent unit: Maybe we can borrow something from the BHD
  • ADC CHs
    • c1ioo seems to have just 8 more spare channels.
    • Borrow a card from bhd? This will require an AI. But their location would be close to the final positions.
  17216   Wed Oct 26 16:04:12 2022 PacoSummaryBHDLO phase control with RF + audio sidebands

[Yuta, Paco]

Today we again locked the LO phase with BH55 + Audio dithering under a zero-offset MICH


We worked with MICH locked using AS55_Q with an offset = 0. Our BH55_Q_ERR is the same as in the previous elog (in this thread).We reduced the MICH offset from 50 to 0 slowly and kept an eye on the BH55 error signals. We realized that at zero offset, most of the error signal was in BH55_I_ERR (why?) so we rotated it back to BH55_Q_ERR (146 deg --> 56 deg). We then looked at the audio demod angle, and optimized it to allocated the error signal in the I quadrature (-15 deg --> 40 deg).


We close a loop with the above configuration to lock the LO phase using only filters FM5, FM8 and then optionally boost with FM2. The measured UGF ~ 20 Hz similar to the configuration with an offset present; and it seems there is some residual noise at ~ 20 Hz (observed in the residual error signal time trace with ndscope).

Next tasks:

  • Noise budget residual error in this configuration
  • Investigate negative count offset in DCPDs
  • Investigate why does the rotation angle change from single bounce to MICH?
  17215   Wed Oct 26 10:28:05 2022 PacoUpdateIOOHEPA ON / WFS ON

Turned HEPA ON this morning at 10:28 local (pacific time) or gpstime = 1350802758. WFS ON right after that. IMC was locked and nominally aligned at this time.

  17214   Tue Oct 25 22:24:46 2022 KojiUpdateIOOHEPA OFF / WFS OFF

Turned HEPA OFF / Lab Lights OFF / WFS Input Gain switched off for the IMC WFS signal tests.
The IMC is still well aligned.

Clean data from the following time:
2022/10/26 5:24:00 UTC (10/25 22:24 PDT)
GPS 1350797056


  17213   Tue Oct 25 22:01:53 2022 ranaConfigurationPEMAuto Z on trillium interface board

thanks, this seems to have recentered well.

It looks like it started to act funny at 0400 UTC on 10/24, so thats 9 PM on Sunday in the 40m. What was happening then?


Attachment 1: Screen_Shot_2022-10-26_at_4.45.30_PM.png
  17212   Tue Oct 25 17:27:11 2022 PacoSummaryBHDLO phase control with RF + audio sidebands

[Yuta, Paco]

Today we locked LO phase with BH55 + Audio dithering


We worked with MICH locked using AS55_Q with an offset = 50. Our BH55_Q_ERR is the same as in the previous elog (in this thread). We enabled audio dithering of AS1 to produce 280.54 Hz sidebands (exc gain = 15000). We used ELP80 (elliptic, 4th order lowpass with the second resonant notch at 280.54 Hz) at the BH55_Q_AS1_DEMOD_I output. This allowed us to generate an error signal to feedback into AS1 POS. Attachment #1 shows a screen capture of this configuration.


We close a loop with the above configuration to lock the LO phase using only filters FM5, FM8 and then optionally boost with FM2. The compromise we had to make because of our phase margin was to achieve UGF ~ 20 Hz (in contrast with ~ 70 Hz used in single bounce). Attachment #2 shows the measured OLTFs for LO_PHASE control using this scheme; the red was the final measured loop, while the blue was our initial reference before increasing the servo gain.


Attachment 1: Screenshot_2022-10-25_17-36-45_LOPHASELOCKED.png
Attachment 2: Screenshot_2022-10-25_17-33-33_LOPHASELOCKING_MICHBHD_ELP80_280HzDither.png
  17211   Tue Oct 25 14:29:56 2022 PacoSummarySEIEarthquake tripped SUS

[Yuta, Paco, JC]

This eq  potentially tripped ETMY, PR2, PR3, AS1, AS4, SR2, LO1, LO2 suspensions during today's WB meeting. We restored them into normal local damping.

We aligned the arm cavities just to verify things were ok and then moved on to BHD comissioning. No problems spotted so far.

  17210   Tue Oct 25 13:55:37 2022 KojiConfigurationPEMAuto Z on trillium interface board

This nicely brought the sensing signal back to ~zero. See attachment

Some basic info:

  • BS Seismometer is T240 (Trillium)
  • The interface unit is at 1X5 Slot 26. D1002694
  • aLIGO Trillium 240 Interface Quick Start Guide T1000742
Attachment 1: Screen_Shot_2022-10-25_at_13.56.46.png
  17209   Tue Oct 25 09:57:34 2022 PacoConfigurationPEMAuto Z on trillium interface board

I pressed the Auto-Z(ero) button for ~ 3 seconds at ~9:55 local (pacific) time on the trillium interface on 1X5.

  17208   Tue Oct 25 08:25:00 2022 JCUpdateBHDBHD fringe aligned with reduced LO and AS beam clipping

I aligned today using this scheme. I couldn't seem to get C1:IOO-MC_TRANS_SUM above 13400 by using WFS or manually aligning. The original state before was the following:
                  Pitch       Yaw     
    -0.4672     -0.7714
C1:SUS-MC2:      4.0446     -1.3558
C1:SUS-MC3:     -2.0006      1.6001


  17207   Tue Oct 25 05:26:24 2022 ranaSummaryIOOMC SUS tuning

in looking closer at the IMC WFS performance I notice 2 issues:

  1. the watchdog thresholds are set to 200 mV, but this only made sense back when the OSEM calibration was 2 V/mm. Because of the increased analog gain(?) the RMS value of the watchdog sensors is now ~35 mV for MC1, so it will trip its watchdog and unlock the IMC with a 10x smaller seismic impulse than before. I recommend changing the watchdog thresholds appropriately changing the OSEM sensor signals to something so that its the same for all SUS.
  2. For the MC SUS, the F2P or F2A decoupling filters are not on. SO the POS damping loop is injecting a lot of pitch noise into the mirrors. We could perhaps lower the ~1 Hz angular motion by commissioning those filters for the MC optics. Does anyone know why we have several filters in those filter banks? I think we could contain it all in 1, although its fine to make a few different ones with different Q's for testing the performance.
  17206   Mon Oct 24 18:01:00 2022 PacoSummaryBHDBHD actuation measurements

[Yuta, Paco]

Today we calibrated the actuation on BHD suspended optics: LO1, LO2, AS1, AS4.
Actuation transfer functions for these optics look good.

ITMY actuation

For a reference we locked LO-ITMY single bounce using the LSC MICH loop. The error point was BH55_Q, the whitening filter gain was 45 dB, IQ demod rotation angle = 151.061 deg, the servo gain was -10, and the actuation point was ITMY. The measured UGF for this loop was ~ 150 Hz when FM2, 3, 4, 5 and 8 were all enabled. Note FM8 is an elliptic low pass (600 Hz cutoff).

LO1, LO2, AS1, AS4 actuation

We then lock the LO phase by feeding back BH55_Q_ERR to the actuation points under test with exactly the same filters but a servo gain of 0.6 but otherwise we are using the same servo filters FM2, 3, 4, 5 and 8 for this controls. The measured UGFs were all near ~ 70 Hz.

Here we had to be careful not to excite mechanical (?) resonances similar to the previously observed "violin" modes in LO1. In particular, we first noticed unsupressed 816 Hz noise in AS1 was being reinjected by the loop sometimes tripping the local damping loops, so we added bandstop filters at the AS1_LSC output filter bank. The resulting loop was then allowed to increase the gain and turn on FM2 and FM3 (boosts). This was also the case in AS4, where 268 Hz and second + third harmonics appeared to be excited by our feedback control. Finally, AS4 also displayed some mechanical excitation at 96.7 Hz, which seemed too low to be a "violin" mode, and its "Q" factor was not as high. We added a bandstop for this as well.

Attachment #1 shows LO_PHASE OLTFs when actuating in the different optics. By taking the actuation ratios (Attachment #2) with respect to our ITMY actuation reference and which had previously been calibrated to be 4.74e-9 / f^2 m / cts, we now have estimated our BHD suspension actuation calibrations to be:

  • LO1 = 3.14e-8 / f^2 m / cts
  • LO2 = 2.52e-8 / f^2 m / cts
  • AS1 = 3.14e-8 / f^2 m / cts
  • AS4 = 2.38e-8 / f^2 m / cts

This magnitudes are consistent with the expected coil driver ranges (about a factor of 10 difference).

Attachment 1: OLTF_LOPhaseLocking_ITMYSingleBounce.png
Attachment 2: ActuationRatio_ITMY_AS1_AS4_LO1_LO2.png
  17205   Sat Oct 22 21:36:28 2022 ranaSummaryBHDBH55 phase locking efforts

give us an animated GIF of this cool new tool! - I'm curious what happens if you look at 2 DoF of the same suspension. Also would be cool to apply a bandpass filter before plotting XY, so that you could look for correlations at higher frequencies, not just seismic noise


Using xyplot tool, we tried to see the relationship between C1:HPC-BHDC_DIFF_OUT and C1:HPC-BH55_Q_DEMOD_I_OUT. The two signals, according to our theory, should be 90 degrees out of phase and should form an ellipse on XY plot. But what we saw was basically no correlation between the two.

  17204   Fri Oct 21 16:15:10 2022 yutaSummaryBHDLO phase locking with BH55 audio dither trials

[Paco, Yuta]

We are still struggling with locking LO phase in MICH or ITM single bounce with BH55 with audio dither.
Without audio dither, BH55 can be used to lock.

What works:
 - LO phase locking with ITMX single bounce, using BH55_Q
  - BH55_Q configuration: 45 dB whitening gain, with whitening filter on.
  - C1:LSC-BH55_PHASE_R=147.621 deg gives most signal in BH55_Q.
  - LO phase can be locked using BH55_Q, C1:HPC-LO_PHASE_GAIN=-0.5 (bright fringe for A, dark for B), feeding back to LO1 gives UGF of ~80Hz (funny structure in ~20 Hz region; see Attachment #1)

 - LO phase locking with ITMX single bounce, using BHDC_DIFF
  - BHDC B/A = 1.57 (gain balanced with C1:HPC-IN_MTRX)
  - LO phase can be locked using BHDC_DIFF, C1:HPC-LO_PHASE_GAIN=-0.4 (mid-fringe lock), feeding back to LO1 gives UGF of ~50 Hz (see Attachment #2).

 - LO phase locking with MICH locked with AS55_Q, using BH55_Q
  - AS55_Q configuration: 24 dB whitening gain, with whitening filter off
  - C1:LSC-AS55_PHASE_R=-150 deg gives most signal in AS55_Q
  - MICH can be locked using AS55_Q, C1:LSC-MICH_GAIN=-10, C1:LSC-MICH_OFFSET=30 (slightly off from AS dark fringe), feeding back to 0.5*BS gives UGF of ~100Hz (see Attachment #3)
  - LO phase can be locked using BH55_Q, C1:HPC-LO_PHASE_GAIN=-0.8 (bright fringe for A, dark for B), feeding back to LO1 gives UGF of ~45Hz (see Attachment #4)

 - LO phase locking with MICH locked with AS55_Q, using BHDC_DIFF
  - LO phase can be locked using BHDC_DIFF, C1:HPC-LO_PHASE_GAIN=1 (mid-fringe lock), feeding back to LO1. Not a very stable lock.

What does not work:
 - LO phase locking using BH55_Q demodulated at LO1 (or AS1) dither frequency, neither in ITMX sigle bounce or MICH locked with/without offset using AS55_Q
  - C1:HPC-AS1_POS_OSC_FREQ=142.7 Hz, C1:HPC-AS1_POS_OSC_CLKGAIN=3000, C1:HPC-BH55_Q_AS1_DEMOD_PHASE=-15 deg, BLP30 is used.
  - Attachment #5 shows error signals when LO phase is locked with BH55_Q. BHDC_DIFF and BH55_Q_AS1_DEMOD_I having some coherence is a good indication, but we cannot lock LO phase with BH55_Q_AS1_DEMOD_I yet.
  - Also, injection at 13.14 Hz with an amplitude of 300 for AS1 can be seen in both BH55_Q and BH55_Q_AS1_DEMOD_I (26 Hz peak for BHDC_DIFF, as it is quadratic, as expected), which means that BH55_Q_AS1_DEMOD_I is seeing something.

 - Check actuation TFs for LO1, LO2, AS1 too see if there are any funny structures at ~ 20 Hz.
 - LO phase locking might require at least ~50 Hz of UGF. Use higher audio dither frequency so that we can increase the control bandwidth.
 - Check analog filtering situation for BHDC_A and BHDC_B signals (they go minus when fringes are moving fast)

Attachment 1: Screenshot_2022-10-21_15-33-18_LO_OLTF_LO1_BH55_Q.png
Attachment 2: Screenshot_2022-10-21_15-42-50_LO_OLTF_LO1_BHDCDIFF.png
Attachment 3: Screenshot_2022-10-21_15-44-53_MICH_OLTF.png
Attachment 4: Screenshot_2022-10-21_15-50-43_LO_OLTF_LO1_BH55_Q_MICH.png
Attachment 5: Screenshot_2022-10-21_16-11-16.png
  17203   Fri Oct 21 10:37:36 2022 AnchalSummaryBHDBH55 phase locking efforts

After the amplifier was modified with a capacitor, we continued trying to approach locking LO phase to in quadrature with AS beam. Following is a short summary of the efforts:

  • To establish some ground, we tested locking MICH using BH55_Q instead of AS55_Q. After amplification, BH55_Q is almost the same level in signal as AS55_Q and a robust lock was possible.
  • Then we locked the LO phase using BH55_Q (single RF sideband locking), which locks the homodyne phase angle to 90 degrees. We were able to successfully do this by turning on extra boost at FM2 and FM3 along with FM4 and FM5 that were used to catch lock.
  • We also tried locking in a single ITMY bounce configuration. This is a Mach-Zehnder interferometer with PR2 acting as the first beam splitter and BHDBS as the recombination beamsplitter. Note that we failed earlier at this attempt due to the busted demodulation board. This lock worked as well with single RF demodulation using BH55_Q.
  • The UGF achieved in the above configurations was ~15 Hz.
  • In between and after the above steps, we tried using audio dither + RF sideband, and double demodulation to lock the LO phase but it did not work:
    • We could see a good Audio dither signal at 142.7 Hz on the BH55_Q signal. SNR above 20 was seen.
    • However, on demodulating this signal and transferring all signal to C1:HPC-BH55_Q_DEMOD_I_OUT, we were unable to lock the LO phase.
    • Using xyplot tool, we tried to see the relationship between C1:HPC-BHDC_DIFF_OUT and C1:HPC-BH55_Q_DEMOD_I_OUT. The two signals, according to our theory, should be 90 degrees out of phase and should form an ellipse on XY plot. But what we saw was basically no correlation between the two.
    • Later, I tried one more thing. The comb60 filter on BH55 is not required when using audio dither with it, so I switched it off.
      • I turned off comb60 filters on both BH55_I and BH55_Q filter modules.
      • I set the audio dither to 120 Hz this time to utilize the entire 120 Hz region between 60 Hz and 180 Hz power line peaks.
      • I changed the demodulation low pass filter to 60 Hz Butterworth filter. I tried using 2nd order to lose less phase due to this filter.
      • These steps did not fetch me any different results than before, but I did not get a good time to investigate this further as we moved into CDS upgrade activities.
  17202   Thu Oct 20 19:47:24 2022 TegaUpdateCDSRelocate front-ends to Rack 1X7

We mounted chiara, all front-end machines and switches in rack 1x7; reconnected power, dolphin, onestop and timing cables; and restarted the front-ends. Attachments 1 & 2 show the front and rear of rack 1X7. We are going to continue the clean up work tomorrow.


The ifo is not back up as can be seen in attachment 3. We think the timing issue mentioned earlier is the culprit, but all FEs seem to agree to within a second, so I am not sure. I restarted the models with iop errors other than the timing error, i.e. c1lsc, c1sus, c1ioo and c1iscex. This eliminated most of the errors but the timing error. However, the overflow field on c1lsc is non-zero and the number keeps increasing - indicating a problem with c1lsc? The new status is shown in attachement 4. My understanfin is the a red `TIM` flag in the CDS stateword is not a functional problem, so I guess we are almost there. I did a burt restore on rossa using a snapshot we took earlier today before the shutdown, reset the SUS watchdogs and started the docker services on optimus. Now the IMC is locked.


We are still getting shared memory glitch on c1ioo, see attachment 5.

Note: We left nodus, megatron, optimus and fb1 in rack 1X6 for now.


Attachment 1: IMG_20221020_193623269.jpg
Attachment 2: IMG_20221020_193637034.jpg
Attachment 3: iop_status_20221020.png
Attachment 4: iop_status_20221020_restart_models.png
Attachment 5: c1ioo_shm_glitch.png
  17201   Thu Oct 20 14:13:42 2022 yutaSummaryPSLPMC and IMC sideband frequencies measured

I measured the sideband frequencies for PMC and IMC lock (to use it for Mariner PMC and IMC design).

PMC: 35.498912(2) MHz
IMC: 29.485038(2) MHz

 - Mini-Circuits UFC-6000 was used. The spec sheet says the frequency accuracy in 1-40 MHz is +/- 2 Hz.
 - "29.5 MHz OUT" port of 40m Frequency Generation Unit (LIGO-T1000461) was connected to UFC-6000 to measure IMC sideband frequency.
 - "LO TO SERVO" port of Crystal Frequency Ref (LIGO-D980353) was connected to UFC-6000 to measure PMC sideband frequency.
 - It seems like IMC sideband frequency changed from 29.485 MHz to 29.491 MHz back in 2011 (40m/4621). We are back to 29.485 MHz. I'm not sure what happened after this.

Attachment 1: IMC.JPG
Attachment 2: PMC.JPG
  17200   Wed Oct 19 11:09:20 2022 RadhikaUpdateBHDBH55 RF output amplified

[Anchal, Radhika]

We selected a 102K (1 nF) ceramic capacitor and a 100 uF electrolytic capacitor for the RF amplifier power pins. I soldered the connections and reinstalled the amplifier [Attachments 1, 2].


1) please remember to follow the loading and power up instructions to avoid destroying our low noise RF amplifiers. Its not as easy as powering up any usual device.

2) also, please use the correct decoupling capacitors at the RF amp power pins. Its going to have problems if its powered from a distant supply over a long cable.


Attachment 1: IMG_3840.jpeg
Attachment 2: IMG_3847.jpeg
  17199   Wed Oct 19 09:48:49 2022 AnchalUpdateOptimal ControlIMC open loop noise monitor

Turning WFS loops back on at:

PDT: 2022-10-19 09:48:16.956979 PDT
UTC: 2022-10-19 16:48:16.956979 UTC
GPS: 1350233314.956979

  17198   Tue Oct 18 20:43:38 2022 AnchalUpdateOptimal ControlIMC open loop noise monitor

WFS loops were running for past 2 hours when I made the overall gain slider zero at:

PDT: 2022-10-18 20:42:53.505256 PDT
UTC: 2022-10-19 03:42:53.505256 UTC
GPS: 1350186191.505256

The output values are fixed to a good alignment. IMC transmission is about 14100 counts right now. I'll turn on the loop tomorrow morning. Data from tonight can be used for monitoing open loop noise.

  17197   Tue Oct 18 15:24:48 2022 TegaUpdateCDSRack 1X7 work proposal

We have decided to split the remaining CDS work on rack 1x7 into two phases, both of which end with us bringing the 40m systems back up.


Phase 1 (Clear rack 1X7 of all mounted pieces of equipment)

  • Move nodus to 1X6 bottom slot
  • Move optimus to 1X6 (replaces old fat FB which can be moved to storage)
  • Move DAQ and network switches to the top of 1X7 rack
  • Move the UPS to under 1X6
  • Clear 1X7 power rail of any connections


Phase 2 (Replace the mounting rails and mount all pieces of equipment)

  • Mount DAQ, network and Dolphin switches at the top rear of 1x7 rack
  • Mount 6 new front-ends
  • Mount KVM switch
  • Move nodus back to 1X7
  • Move optimus back to 1X7


  17196   Mon Oct 17 22:27:25 2022 ranaUpdateBHDBH55 RF output amplified

1) please remember to follow the loading and power up instructions to avoid destroying our low noise RF amplifiers. Its not as easy as powering up any usual device.

2) also, please use the correct decoupling capacitors at the RF amp power pins. Its going to have problems if its powered from a distant supply over a long cable.

  17195   Mon Oct 17 20:04:16 2022 AnchalUpdateBHDBH55 RF output amplified

[Radhika, Anchal]

We have added an RF amplifier to the output of BH55. See the MICH signal on BH55 outputs as compared to AS55 output on the attached screenshot.


Next steps:

- Amplify the BH55 RF signal before demodulation to increase the SNR. In order to power an RF amplifier, we need to use a breakout board to divert some power from the DB15 cable currently powering BH55.



  • Radhika first tried to use ZFL-500-HLN+ amplifier taken out from the amplifier storage along X-arm.
  • She used a DB15 breakout board to source the amplifier power from PD interface cable.
  • However, she reported no signal at the output.
  • We found that BH55 RFPD was not properly fixed tot eh optical table. We bolted it down properly and aligned the beam to the photodiode.
  • We still did not see any RF output.
  • I took over from Radhika on this issue. I tested the transfer function of the amplifier using moku:lab. I found that it was not amplifying at all.
  • I brought in a beanchtop PS and tested the amplifier by powering it directly. It drew 100 mA of current but showed no amplififcation in transfer function. The transfer function was constant at -40 dB with or without the amplifier powered.
  • I took out another RF amplifier from the same storage. This time a ZFL-1000-LN. I tested it with both benchtop PS and PD interface power source, it was wokring with 20 dB amplification.
  • I completed the installation and cable management. See photos attached.
  • I also took the opportunity to center the ITMY oplev.

Please throw away malfunctioning parts or label them malfunctioning before storing them with other parts. If we have to test each and every part before installation, it will waste too much of our time.


Attachment 1: BH55_RF_Amp_Working.png
Attachment 2: rn_image_picker_lib_temp_1b072d08-3780-4b1d-9325-5795ed099d3d.jpg
Attachment 3: rn_image_picker_lib_temp_9d7ed3c0-7ff0-4ff7-9349-0211be397dc5.jpg
Attachment 4: rn_image_picker_lib_temp_05da14e1-eae0-4a84-8761-1c42b122cb1b.jpg
  17194   Mon Oct 17 17:42:35 2022 JCHowToOPLEV TablesIMC Reflected beam sketch

I sketched up a quick drawing with estimated length for the IMC reflected beam. This includes the distances and focal length. Distances are from optic to optic. 

Attachment 1: Screenshot_2022-10-18_093033.png
  17193   Mon Oct 17 11:57:27 2022 ChrisOmnistructureCDSTiming system monitoring

I started a GPS timing monitor script, /opt/rtcds/caltech/c1/Git/40m/scripts/cds/tempusTimingMon/tempusTimingMon.py, which runs inside a docker container on optimus. It accesses the GPS receiver (EndRun Tempus LX) status via pysnmp, and creates the following epics channels with pcaspy:

  • C1:DAQ-GPS_TFOM “The Time Figure of Merit (TFOM) value ranges from 3 to 9 and indicates the current estimate of the worst case time error. It is a logarithmic scale, with each increment indicating a tenfold increase in the worst case time error boundaries.” (nominally 3, corresponding to 100 nsec)
  • C1:DAQ-GPS_STATE “Current GPS signal processor state. One of 0, 1 or 2, with 0 being the acquisition state and 2 the fully locked on state.”
  • C1:DAQ-GPS_SATS “Current number of GPS satellites being tracked.”
  • C1:DAQ-GPS_DAC “Current 16 bit, Voltage Controlled TCXO DAC value. Typical range is 20000 to 40000, where more positive numbers have the effect of raising the TCXO frequency.”
  • C1:DAQ-GPS_SNR “The current average carrier to noise ratio of all tracked satellites, in units of dB. Values less than 35 indicate weak signal conditions.”

Attached is a 1-day trend of the above channels, along with the IRIG-B timing offsets from the IOPs. No big timing excursions or slippages were seen yet, although the c1sus IOP (FEC-20) timing seems to be hopping around by one IOP sample time (15 µsec).

Attachment 1: timing.png
ELOG V3.1.3-